Various types of track-suspended door structures are known. For example, U.S. Pat. No. 3,266,189 shows a typical power-operated arrangement. It is known to so arrange sliding doors that the doors can move not only in direction of a suspension track, for example in a straight line to and from each other, but additionally include panel members which are arranged for swinging movement transverse to the direction of sliding movement. Such additional swinging movement is desirable particularly in installations where a maximum panel opening is desired, for example to permit a large number of people to rapidly leave a building, or to provide an opening of increased width for vehicular traffic. Residential applications whereby the user desires maximum view and ventilation are also to be appreciated. However, sliding doors which are so arranged cause difficulties since swinging movement of the door panels or door elements of sliding doors does not permit attaching of hinges about which the doors can swing to a fixed frame. The attachment point for the hinges are movable and for swinging movement the doors can no longer be supported along their width from the top. For example, the hinge attachment on a sliding frame portion will shift, causing the door, as it swings, to bind against a floor structure. It is customary to provide sliding doors with a downwardly projecting guide element, typically a bolt, or the like, which slides in a guide track or rail. This bolt, however, is movable longitudinally in a sliding direction and will shift its position upon release of a swinging door element from the sliding door structure, so that it is suspended only on the hinges, due to the force moment which the door exerts on the hinge structure. It is undesirable to foreshorten the door so that the tilting of the door frame, upon swinging movement of the door, is compensated, since, then, when the door is closed, a gap will permit exchange of heated or cooled air, and otherwise interfere with the purposes of a door, which is to close off an opening.
U.S. Pat. No. 4,438,594 uses a massive metal angle element to provide a pre-stressing force and keep the door panel from binding with the floor structure ort to counteract the weight as the panels swing open. This type of counterweight would add considerably to the weight of the door and require more strength to push the panel open or closed. Massive counterweights require reinforcements in the building frame and door jamb to hold the additional weight. A massive counterweight would require heavy duty bogies, guide tracks, and pivot hinges to carry the weight. Shipping would also be more expensive due to the additional weight. Installation of the door panels would require more manpower to hold up the “massive counterweight” while installers secure the panels to the bogies. The added shipping weight, manufacturing cost and labor would be cost prohibitive.
U.S. Pat. No. 5,272,839 uses a toothed apparatus and hinge pins to eliminate friction and weight transfer. The '839 patent also suggests a wing shaped bracket to prevent the pane from tilting. Brackets springs, and toothed apparatus require precision manufacturing and highly trained installers because the panels would need to be aligned perfectly. Toothed apparatuses and wing shaped brackets can wear out easily with repeated use. These disadvantages would add to the cost of manufacturing and installation as well as allowing for more points of failure in the closure.
Bi-folds closure, which are known and have been around since the 1950's. The Nana bi-fold doors manufactured by NanaWall Systems, Inc. or the lanai bi-fold doors, manufactured by Lanai Doors Incorporated, require four to eight hinge mechanisms per panel to stabilize and transfer the weight of the attached open panels to the frame of the building. These many hinges keep the panels from binding against a floor structure. These hinge mechanisms require precise manufacturing and installation because many of the panels are attached together like a train and a failure at one hinge or wheeled carriage bogie effects all the attached panels rendering the door inoperable. With many parts that need to be manufactured and assembled precisely and difficult installation, the costs for these bi-fold closure systems tend to be in the high end or Luxury category. More hinges also create more failure points for these bi-fold closures. Bi-fold closures are limited in their width due to the fact that the more panels that are attached together, the heavier the closure becomes and the harder it is for the consumer to push open a multi panel bi-fold closure because they need to move all the attached weight.
What is needed is a better sliding door structure.